Ticket #23778 -- Add a code snippet in the advanced testing documentatio...

...n showing how to run tests outside de test runner.
This note helps a bit, but I think this section is still unclear in its purpose and thus not very useful. It still conflates "using `manage.py test`" with "using the test runner", as if they are equivalent, when they are not at all equivalent.

I would put this "Running tests outside the test runner" section after your added section about reusable apps, as it's a far less common use case, and replace its entire contents with this:

> If you need to run tests without using Django's :class:`~django.test.runner.DiscoverRunner`, you will need to perform some test environment setup and teardown yourself before and after the test run. The necessary setup code can be found in :func:`django.test.runner.DiscoverRunner.setup_test_environment` and :func:`django.test.runner.DiscoverRunner.setup_databases`. The teardown code can be found in :func:`django.test.runner.DiscoverRunner.teardown_databases` and :func:`django.test.runner.DiscoverRunner.teardown_test_environment`.